Fix WebBluetooth generator to distinguish between different methods.

third_party/WebKit/LayoutTests/bluetooth/script-tests/characteristic/gatt-op-disconnect-called-before.js

 'use strict';
 promise_test(() => {
   let val = new Uint8Array([1]);
   return setBluetoothFakeAdapter('DisconnectingHealthThermometerAdapter')
     .then(() => requestDeviceWithKeyDown({
       filters: [{services: ['health_thermometer']}]}))
     .then(device => device.gatt.connect())
     .then(gattServer => {
       return gattServer.getPrimaryService('health_thermometer')
         .then(service => service.getCharacteristic('measurement_interval'))
         .then(measurement_interval => {
           gattServer.disconnect();
           return assert_promise_rejects_with_message(
             measurement_interval.CALLS([
               readValue()|
               writeValue(val)|
               startNotifications()|
               stopNotifications()]),
             new DOMException(
               'GATT Server is disconnected. Cannot perform GATT operations.',
               'NetworkError'));
         });
     });
 }, 'disconnect() called before FUNCTION_NAME. Reject with NetworkError.');